Lock-stitch sewing machine



May 11 1926.

M. HEMLEB LOCK STITCH SEWING MACHINE Original Filed July 6, 1923 2 Sheets-Sheet 1 INVENTOR ATTORNEY May 11., 1926. 1,583,925

M. HEMLEB I Ldcx STITCH SEWING MACHINE Original Filed y 16, 1925 2 Sheet-Sheet 2 INVENTOR WITNE ES BY y I ATTORNEY Patented -May 11, 1926.

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MARTIN HEMLEB, OF ELIZABETH, NEW JERSEY, ASEEGNOR '10 TEE SINGER, MANU- FAGTUBING COMPANY, OF ELIZABETH,

JERSEY.

llliilti' JERSEY, A CGRIORATION 0F NEW LOCK-STITCH SEWING MACHINE.

Original application filed July 16, 1328, Serial E0. 651,800. Divide-cl and. this application filed March 13,

1924. Serial No. 698,824.

This invention relates to lock-stitch sewing machines, more particularly of the type having a hook which rotates at a. uniform speed and a needle-bar which is actuated by the usual crank and pitman, so as to have substantially a simple harmonic motion, the same as the piston-rod of an ordinary steam engine. Machines of the type in question have been constructed to sew satisfactorily and without tendency to overheat at speeds of from 3,500 to 000 stitches per minute but have had a bobbin capacity limited to about 7 5 yards of No. 90 cotton. With such machines, however, it has heretofore been considered necessary to employ a rotary take-up and to provide means for manually adjusting the take-up to suit the thickness oi work to be sewed. Even with this adj ust ment such machines are only able to sew work varying from thin to medium thickness.

In all prior lock-stitch machines with which I am familiar, conditions are such that there is a delay in the take-up action V upon the needle-loop, considerable slack remaining in such loop as the needle starts down. This delay is largely responsible for chafing of the needle-thread by the point of the needle which, under the conditions noted, is descending simultaneously with the ascent of the. needle-thread pulled from the needleloop by the take-up. Since the take-up must finish its take-up action and give slack for the needle-eye to double through the work, it follows that a delayed take-up action necessitates a delayed slaclcgiving; action and hence it has been necessary to delay the time when the needle-eye reaches the work by increasing the stroke ofthe needle-bar above the work. Such increase. in the. stroke of the needle-bar increases vibration, reduces the speed at which the machine can be satisfactorily operated and increases the distance between the needle-eye and the work during the take-up action, thus increasing the danger of the upwardly moving needlethread whipping or vibrating late ally suiticiently to be caught or chafed by the needle point.

Furthermore, the rotary take-up has .a serious disadvantage, in that, in. case of thread breakage, it irequently catches the thr ten leadin a hejsreel and. were off a considerable quantity of thread before the machine can be stopped.

The present invention has for an object to provide a machine which will sew work of greater variation in thickness than has heretofore been considered feasible at speeds oi from 3500 to 4000 stitches per minute, and which will sew from the thinnest to the thickest work a range of about five-sixteenths of an inch) at these speeds without in anual adj ustment.

Another object of the invention is to provide a high-speed lock-stitch sewing machine having an increased bobbin-thread capacity.

Another ob]ect of the invention is to provide a rotary hook sewing machine having the parts so combined and related as tocomplete the taking up of the slack in the needle loop after has been cast about the. bobbin and before the needle begins its down stroke, therebyminimizing the danger of the needlepoint chafing the thread and effecting substantially the complete take-up of the needleloop during the latter part of the up-stroke of the needle with the consequent important.

advantage of being able to sew work of maximum thickness with a minimum needlestroke.

, I have found by experimentation that by combining a cranleand-link operated takeup with a rotary hook making three revolutions for each complete reciprocation of the needle-bar, I am enabled to effect the taking up of the needle-loop by substantially the time the needle reaches its highest pointand to effect the. slackening of the thread considerably earlier in the down-stroke of the needleloar than has heretofore been attained, Inasmuch as the thickness of the work which a machine of the type in question will sew is limited by the distance. of the needle-eye above the throat-plate at the time of slaoken ing. of the thread by the takeup, it follows that I am thus enabled to sew work up to a maximum thickness with a minimum needlebar stroke, which latter is an important dcsideratum or ahighspeedmachine. Further, by the combination in question, I find that the larger needle-loop occasioned by the in:

creased siz e of the bobbin can be successfully handled in the aforesaid manner at the high speeds contemplated,

la the weath ring was lit longitudinal vertical section through the frame of a sewing machine embodying the invention. Fig. 2 illustrates the relative positions of the needle-bar and link take-up at the beginning of the take-up action. Fig. 3 illustrates the relative positions of the needlebar and take-up when the needle-loop has been drawn up to the work. Fig. l illustratcs the take-up ready to give slack early in the down-stroke of the needle-bar. v

In the embodiment of the invention illustrated, 1 represents the bed-plate of a sewing machine from which rises the standard 2 of the bracketarm 3 terminating in the head a. The. main-shaft 5 is journaled in the arm 3 and at its forward end carries the needlebar and take-up operating cranks 6, 7, re-

spectively, which, in accordance with the present improvement, are set quite close together, so as to be substantially coincident. The needle-bar crank 6 is directly connected by means of the usual link 8 to the needlebar 9 which carries the eye-pointed needle 10, and drives the latter with substantially a simple harmonic motion, such as is ordinarily communicated to a reciprocating bar by the usual unmodified crank-and-pitman drive.

The main-shaft 5 carries the usual balance-Wheel 11 and has secured thereto the bevel-gear 12 which meshes with the gear 13 on the upper end of the vertical shaft 14; carrying at its lower end the bevel gear 15 which meshes with the gear 16 on the hookshaft 17 journaled in bearings 18 below the bed 1. The gear-ratios are so chosen that the hook-shaft 17 is given three rotations to one rotation of the main-shaft 5. The bearings 18 are preferably constructed in accordance with the disclosure of my copending application Serial No. 651,802, filed July 16, 1923. The three-to-one hook is carried by the shaft 17 and preferably comprises the cup-shaped body 19 formed with the usual oblique cut 20 defining the hook-beak 21. The bobbin and its case 22 may be supported within the open raceway of the hook, without resting upon the latter, in the manner fully disclosed in my application Serial No. 651,800, filed July 16, 1923, of whichthis application is a division.

The take-up is of the so-called link. or crank-and-link operated type and comprises the usual angle-lever having rigidly related arms 23, 24, the former of which embraces the take-up operating crank 7 and the latter of which is formed with the thread-eye 25. The lever 23, 2a, is pivotally connected at the juncture of its arms to one end of the anchor link 26, the opposite end of which is pivoted at 27 to the lug 28 within the head 4. By referring to Figs. 2, 3 and 4 it will be noted that the centers of the cranks 6 and 7 are substantially coincident; the

needlerbar era-11k 6 being in the embodiment of the invention, herein illustrated, set slightly in advance of the take-up crank 7 and slightly nearer the main-shaft 5 than the crank 7. The take-up is thus caused to give slack before the needle-eye has descended a material distance, i. e., before the needle-eye has descended a distance corresponding to the distance between the latter and the needle-point. Consequently the machine will successfully sew work as thick as the needle point will clear.

The tension device is of common form and comprises the separate disks 29 which are yieldingly pressed together by the spring 30 upon the thread passing between them to frictionally retard the feed of such thread. The tension device also has associated therewith the usual light check-spring 31 which yields thread to the take-up as the latter completes its up-stroke after having drawn up the. needle-loop. The spring 31 also takes up the slack given up by the take-up eye in the clown-stroke of the needle and prevents the formation of slack below the eye of the needle, particularly when sewing thin work. Fixed to the presser-bar is the arm 32 which extends under the check-spring 31 and determines the lower limit of the movement of the latter in accordance with the thickness of the work. I 8

Operation.

The needle-loop is seized from the needle, spreadand carried around the bobbin to cast off position, Fig. 2, in the usual manner. The take up now operates rapidly to draw up the loop; allowing but little slack in the loop as the latter follows the loop-arresting heel 33 in the upward movement of the latter. The take-up action Fig. 2 does not start until theneedle-eye has risen to a height of more than five-sixteenths of an inch above the throat-plate and the loop is taken up to the work before the needle starts down, as shown in Fig. 3.

It will be noted with reference to Fig. 3 that although the needle-loop has been taken up to the work, the take-up has not quite reached the limit of its up-stroke. The further upward movement of the take-up lifts the check spring to its upper limit, Fig. 4, and. pulls through the tension device 29 an amount of thread equal to that used in making the preceding stitch. hen sewing thicker work the arm 32 is elevated and lifts the spring 31 a corresponding amount, thus reducing the distance said spring will be lifted by the take-up. The take-up is thus caused to pull a greater amount of thread from the supply. By reference to Fig. 4 it will be seen that the take-up starts to give slack very early in the down-stroke of the needle so that slack thread is provided for doubling by the needleeye through the thickest work that the needlepoint will clear. I am thus enabled to reduce the length of the needle-stroke to a minimum for sewing work up to a given thickness. So far as I am aware this desirable result has not heretofore been attained.

Having thus set forth the nature of the invention, what I claim herein is 1. In a lock-stitch sewing machine, the combination with a reciprocating eyepointed needle having substantially a simple harmonic motion, and a rotary hook making at a uniform speed three rotations for each reciprocation of the needle, of a crank-andlink take-up operating to draw the needleloop up to the work and to give slack before the needle-eye has descended a distance below its upper limit equal to the distance between such eye and the needlepoint.

2. In a lock-stitch sewing machine, the combination with a reciprocating eyepointed needle having substantially a simple harmonic motion and a rotary hook making at a uniform speed three rotations for each reciprocation of the needle, of a crank-andlink take-up operating to draw the needleloop up to the Work before the needle begins its clown-stroke and to give slack before the needle has descended. a distance below its upper limit equal to the distance from the needle-eye to the needle-point.

In a lock-stitch sewing machine, the combination with a reciprocating eye-pointed needle, a needle-bar, a main-shaft having a needle-bar operating crank, a pitman connecting said crank to said needle-bar, and a rotary hook making at a uniform speed three rotations to one reciprocation of the needle, of a bellcrank take-up lever, a takeup operating crank on said main-shaft embraced by one end of said take-up lever, and an anchor link connected to the knee of said take-up lever, the needle-bar crank and the take-up crank being nearly coincident.

In testimony whereof, I have signed my name to this specification.

MARTIN HEMLEB. 

